our company is in the clothing hire business. Ive just started with them and they have no reporting to speak off

Most of thier hire orders fall on Friday and Saturday as thats when the majority of the functions tend to be. they are keen to accurately compare hires for coming months with previous months, the problem they have always faced in doing this is some months have more weekend hire days than others

ie.march 2013 5xfriday & 5xSaturdaymarch 2014 4xfriday & 5xSaturday

is there any clean way to actually do this comparison, or is this only possible if you break the year down into 4 week months starting from the first weekend of the year?

Think of the numbers above as the "Normalized Sales for the Month". If there had been 5 Fridays in 2014, it's likely it would have had 1250 for the month.

The numbers aren't "real" but do indicate, relatively speaking which month did better by taking the number of weeks into consideration. The "5" in both forumlas could be any constant but either 1 or 5 seem to be the easiest to understand. "5" is used to "normalize" all months to a 5 week period. If you use "1" instead, then you end up with the average performance by week for the month. For example...